Collapsible Liquid Tank

ABSTRACT

A collapsible liquid storage tank for use in a freight container for selectively carrying solid freight and bulk liquid freight includes a substantially rigid gantry having a plurality of support posts, a first frame, a second frame suspended from the gantry, a substantially inelastic flexible fabric container having sidewalls connected between the first frame and the second frame, a liquid impermeable elastic bladder disposed within the fabric container and having seals along flat surfaces of the elastic bladder, a centrally positioned outlet, and a hoist coupled between the gantry and the second frame for lifting the second frame towards the first frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of prior U.S. application Ser. No. 12/483,307, filed Jun. 12, 2009.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

REFERENCE TO A “SEQUENCE LISTING”

None

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to collapsible tanks for freight containers that allow the freight container to be converted to selectively carry solid freight or bulk liquid freight, and more particularly to a collapsible tank that is both stronger and easier to clean than heretofore known tanks.

2. Description of Related Art

Collapsible tanks of the general type with which this invention is concerned are shown in U.S. Pat. Nos. 6,015,055; 6,065,265; 6,131,756; 6,216,900; and 6,299,437.

SUMMARY OF THE INVENTION

While the collapsible containers described in the patents mentioned above have been very successful and have provided significant advantages over liquid transfer vessels used in the past, there is a need for such containers that are especially adapted for use in transporting liquids, including but not limited to liquid food products and liquid chemicals, and particularly for containers for storing and transporting liquids, which containers are inexpensive, light, and easy to clean. It is to these characteristics of containers for transporting liquids that the present invention is addressed.

Heretofore, such tanks have employed a flexible inner liner and a flexible outer shell attached to top and bottom frame portions of the tank.

A disadvantage of constructions of the type heretofore used is that it is desirable, for reducing the load on the outer shell and the structure supporting the tank, that the sides and perhaps the bottom of the tank be permitted to swell to a slightly rounded shape when filled with liquid, to reduce stresses on the tank material. For cleaning purposes, it is preferable that the sides and bottom of the tank be relatively flat so that they may be effectively cleaned between uses. Heretofore, the sides and bottom of the tank employed seals along the vertical corners and the perimeter edges of the tank where liquid would collect, making it difficult to clean the tank between uses.

Another disadvantage of tank constructions heretofore used is that liquid pooled in the end corners and would not completely drain out without raising the portion of the tank farthest from the outlet slightly higher than the other end portion of the tank having the outlet.

Briefly stated and in accordance with one aspect of this invention a collapsible liquid storage tank for use in a freight container for selectively carrying solid freight and bulk liquid freight includes a substantially rigid gantry having a plurality of support posts, a first frame, a second frame suspended from the gantry, a substantially inelastic flexible fabric container having sidewalls connected between the first frame and the second frame, a liquid impermeable elastic bladder disposed within the fabric container, and a hoist coupled between the gantry and the second frame for lifting the second frame towards the first frame.

In accordance with another aspect of the invention the collapsible liquid storage tank includes an impermeable elastic bladder that is smaller than a substantially inelastic flexible fabric container when the liquid impermeable elastic bladder is relaxed and larger than the substantially elastic fabric container when the liquid impermeable elastic bladder is expanded so that the expanded size of the bladder is limited by the substantially in the last flexible fabric container.

In accordance with another aspect of the invention the liquid impermeable elastic bladder has a substantially smooth inner surface when not expanded to facilitate cleaning.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a rear elevation of a collapsible storage tank in accordance with this invention shown positioned within the body of a trailer.

FIG. 2 is a top rear perspective view of the upper portion of the gantry and upper frame of a collapsible storage tank in accordance with this invention.

FIG. 3 is an enlarged perspective view of a cleaning portal of a collapsible storage tank in accordance with this invention.

FIG. 4 is a rear elevation of an empty tank in accordance with this invention.

FIG. 5 is a rear elevation of a collapsible storage tank shown filled with liquid in accordance with this invention.

FIG. 6 is a detailed view of the upper attachment portion of the tank in accordance with this invention.

FIGS. 7A and 7B are side elevations partly in section of the collapsible storage tank of this invention, shown empty and full, respectively.

FIG. 8 is an exploded fragmentary view showing the manner in which the fabric container and inner bladder are attached to the frame of the invention showing the substantially inelastic flexible fabric container and the elastic bladder in section.

FIG. 9A is a side elevation showing the lifting mechanism for the collapsible storage tank of this invention.

FIG. 9B is a side elevation showing the collapsible storage tank of this invention in transition from its deployed configuration to a stowed configuration.

FIG. 10 is a rear elevation showing the collapsible storage tank of this invention in transition between the deployed position and the collapsed position.

FIG. 11 is a rear elevation showing the collapsible storage tank of this invention shown in the fully collapsed storage configuration.

FIG. 12 is a rear view, in perspective, showing the storage tank in the stowed position with cargo positioned beneath the tank.

FIG. 13 is a bottom perspective view of an embodiment of the liquid impermeable elastic bladder having diagonal seals.

FIG. 14 is a fragmentary perspective view showing two diagonal seals extending from two corners of an end wall of the liquid impermeable elastic bladder.

FIG. 15 is a front view of a single piece blank for forming an end panel of the liquid impermeable elastic bladder.

FIG. 16 is a perspective view of multiple panels to be sealed together to form the liquid impermeable elastic bladder.

FIG. 17 is a side elevation showing a trailer having the storage tank of this invention in the deployed position.

FIG. 18A is a side elevation showing a trailer having the storage tank of this invention in the emptying position, with a lower portion of the liquid impermeable elastic bladder in a substantially funnel-shaped configuration.

FIG. 18B is a fragmentary side elevation showing the liquid impermeable elastic bladder having a substantially funnel-shaped configuration in the emptying position.

FIG. 19A is a rear elevation of the storage tank shown in the deployed position.

FIG. 19B is a rear elevation of the storage tank shown in the emptying position.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a rear elevation of a collapsible liquid tank 10 in accordance with this invention shown positioned within the body of a trailer used to transport the tank and other cargo. The tank 10 is attached between and supported by upper 12 and lower 14 frame members that are suspended from a gantry 16 that includes a plurality of short vertical supports 17 along each side and an upper gantry platform comprising a plurality of cross beams 18 attached to the upper frame 12. The lower frame 14 is connected to the upper portion of the gantry by cables 34 (see FIG. 2) that permit the frame members to be selectively lowered into a liquid receiving configuration as shown in FIG. 1 or raised to the upper portion of the gantry for storage as shown in FIGS. 10-12. As can also be seen more clearly in FIGS. 2, 9A and B, 11 and 12, the gantry includes intermediate left and right horizontally arranged support rails 19, 21, on which the ends of the plurality of transverse support beams 18 rest when the tank is in the deployed configuration. In a configuration of the invention, the liquid storage tank has an outlet port 20 that may be connected to a hose 22 for emptying the tank while it remains situated within the trailer. The outlet port may be positioned proximate the lower frame member 14 as shown in FIG. 1. Alternatively, the outlet port may be centrally positioned within a floor of a liquid impermeable elastic bladder of the tank as discussed below. Optionally, a plurality of straps (not shown) can be attached between fittings on the floor of the trailer and the upper frame of the tank to retain the tank in position during transport.

FIG. 2 shows the upper portion of the gantry 16 and the upper platform in more detail. The upper frame 12 includes a rectangular outer portion to which the tank material 26 is attached as shown in more detail below and a plurality of transverse members 18 forming the platform 18 secured to the rectangular frame 12. The transverse members 18 are spaced closely enough to permit support plates 30 to be attached thereto for permitting servicepersons to walk along the upper surface of the platform to access the cleaning portal 32 opening into the tank and of sufficient size to receive a cleaning person, or automatic or manual cleaning apparatus. As can be seen in FIG. 2 and also in FIGS. 9A and 9B, the ends of the transverse members 18 rest on the upper surface of the horizontal supports 19 and 21. The upper frame 12 is attached to the transverse members and is supported thereby when the tank is in the deployed position as shown in FIG. 2. The lower frame member 14 is supported by the tank material, and preferably rests on or near the floor of the trailer as shown in FIG. 1.

The gantry includes a plurality of short vertical support members 17, a long double support member 37, 43 at each corner, and a single support member 15 along each side disposed between the double support members. The double support members 37 support the pulleys 42 around which the lifting cables 34, 36 are entrained. The single support members support the horizontal support rails 19 and 21, and also act as guides for the transverse members 18, which, as can be seen in FIGS. 2 and 9, engage the vertical support members 37, 43, 15 on different sides to prevent the upper frame member 12 from swinging to and fro.

Cables 34, 36 are attached to a motorized winch 40 and entrained over pulleys 42 mounted to the upper platform of the gantry and then downwards to the lower support frame 14 for the tank.

FIG. 3 is an enlarged view of the cleaning portal 32 showing a cover 56 mounted to a pivot arm 58 swung out of position to permit a cleaning hose to be inserted into the portal 32. A latch 60 or a plurality of latches positioned around the periphery of the cleaning portal secure the cover in a closed position for transport. Preferably, the portal 32 is sufficiently large to allow a person to enter, or to allow a cleaning apparatus to be inserted into the tank.

FIG. 4 shows the tank of this invention in an empty state in which the outer container is not expanded. Note that although the outer container is not expanded, the liquid impermeable elastic bladder 64, not visible in this view, but visible in FIG. 7A, is relatively smooth on the inside surface, thus facilitating cleaning of the tank.

FIG. 5 is a side elevation similar to FIG. 1 showing the tank in the full condition. The tank 10 includes a substantially inelastic flexible fabric outer container 26 and a liquid impermeable elastic bladder 64 not visible in FIG. 4 or FIG. 5. By providing an outer container 26 that is shaped to allow a slight bulging when filled, the stresses on the outer container are substantially reduced from the stresses that would be present in a rigid container or a container not allowing a slight bulge.

FIG. 6 shows a corner of the upper frame 12 illustrating the manner in which the inner and outer tank materials 64, 26 are connected to the frame. The fabric container 26 and the elastic bladder 64 obscure the upper frame 12 in FIG. 6. The fabric container 26 is preferably provided with a folded over sealed edge 70 forming a compartment through which a rope 72 in the nature of a drawstring or cord or the like is passed to make the upper edge of the fabric container slightly thicker than the fabric itself to prevent it from slipping. The container 26 and the inner bladder 64 are secured to the upper frame 12 by elongated U-shaped battens 74 preferably metal, or a similar structure through which bolts 76 or other fasteners are passed as more clearly shown in the detailed view of FIG. 8.

FIGS. 7A and 7B are partially exploded partially sectioned end views of a collapsible liquid storage tank 10 in accordance with this invention. FIG. 7A shows battens 74 attached to the upper tank support frame 12 and the lower frame 14, and a sectioned view of the inelastic flexible fabric container 26 and the liquid impermeable elastic bladder 64.

As can be seen from FIG. 7A, the substantially inelastic flexible fabric container 26, which is preferably made from Kevlar or a similar inelastic material, has a longer peripheral section than the unexpanded liquid impermeable elastic bladder 64. In this way, the elastic bladder 64 can be readily cleaned when the tank is empty as shown in FIG. 7B. Preferably, but not necessarily, the elastic bladder 64 is at least slightly stretched when the tank is empty so that it presents a smooth surface for cleaning. When the tank is filled, the elastic bladder 64 (but not the substantially inelastic flexible fabric container 26) stretches. The extent of stretching of the elastic bladder 64 is limited by the inelastic flexible fabric container 26. It is not necessary to provide reinforcing materials in the elastic bladder. The inelastic fabric container limits the amount of expansion. This allows a relatively less expensive unreinforced bladder to be employed than has been possible heretofore. Allowing the bladder to stretch to the bowed shape of the inelastic fabric container shown in FIG. 5 reduces the stresses on the fabric container and the bladder, thereby allowing the support frame to be made lighter so as to increase the useful load that can be carried by the tank.

Preferably, the inelastic fabric container 26 and the elastic bladder 64 are secured to the upper and lower frames by a securing rail or batten 74 attached to the frame by a bolt or similar fastener as shown in FIG. 8. The upper attachment 6 is shown exploded for clarity.

FIG. 8 is an exploded view of the upper attachment 6 portion showing the portion of the frame, the U-shaped attachment plate or batten, the bolt 76 and nut 78 in more detail. The inelastic flexible fabric container upper edge portion is preferably provided with an enlarged bead 70 to prevent the fabric layer from slipping out of the clamp. The elastic bladder 64 is preferably provided with a similar bead 86. As shown in FIG. 8, the bolt extends through the batten 74, the fabric container 26, the bladder 64, and the upper frame. As can be seen, both the fabric container and the elastic bladder are held in position by the pressure between the frame element and the batten, as well as by the enlarged edges 70, 86 that prevent the fabric and the bladder from slipping through the space between the frame and the batten. The elastic bladder 64 also preferably has a top portion welded to the side portion to provide substantially complete containment of the fluid contents.

As shown in FIGS. 9-11, the cables 34, 36 extend from winch 40 around the pulleys 42 attached to top caps 35 bridging the dual gantry end supports 43 to attachment points 44 on the lower frame 14. When the cables 34, 36 are retracted to put the tank in the storage position, the lower frame 14 is raised from a position on the floor of the trailer to a position adjacent the top of the gantry 16. The upper frame 12 and transverse members 18, which are preferably not attached to the cables, are raised with the lower frame 14 when the lower frame is lifted.

The ends of transverse members 18 engage the vertical support portions 37, 43, 15 of the gantry 16 to keep the upper frame 12 at least loosely aligned with the gantry. Left and right horizontal support rails 19, 21 support the transverse cross members 18 from which the upper frame 12 is suspended at a position intermediate the top of the gantry 16 and the bottom of the trailer. The rails are attached to the approximate midpoint of the vertical support members of the gantry 16 or alternatively, cables may be attached to the upper frame 12 that permit the upper frame 12 to be lowered into a position only part-way down the gantry structure.

FIGS. 9A and 9B are side elevations of the storage tank of this invention shown in its lowered position, but not filled with liquid. The gantry, vertical supports, and lifting arrangement can be seen in this figure. The cables are entrained around pulleys and attached to an upper portion of the lower frame member 14 for raising the frame member to move the tank from the deployed condition to the stowed condition as shown and described below in connection with FIGS. 10 and 11.

FIG. 9A shows the liquid storage tank of this invention and a deployed configuration. The cables 34 extending over pulleys 42 from winch 40 are fully extended so that the lower frame member 14 essentially rests on the floor of the trailer or at least proximate thereto. The upper frame member 12 is supported by cross members 18, the ends of which rest on side rails 19 and 21. The walkway 30 is supported on the upper surfaces of the cross members 18. The gantry structure can be easily visualized from this view. The dual vertical supports 37 and 43 extend from the floor of the trailer to top caps 35. Supports 37 and 43, as well as the supports on the other side of the structure, not visible in FIGS. 9A and 9B, are preferably strong enough to support the full weight of the empty tank when it is raised from the deployed configuration to the stored configuration. Aluminum or steel tubes, round or other configuration, may be used.

A plurality of shorter vertical supports 17 extend from a bottom rail 90 mounted or resting on the floor of the trailer to intermediate horizontal support rails 19 and 21. Note that the intermediate rails 19 and 21 may be formed in one or more pieces that are attached to the tops of the vertical supports and/or interrupted and welded thereto.

As can be seen from FIGS. 9A and 9B, the transverse members 18 are spaced such that different members are disposed on different sides of the vertical gantry members 37, 15, 43. This arrangement substantially prevents the tank frame from swinging longitudinally, that is in the left-right direction as seen in FIGS. 9A and 9B, as the tank is raised and lowered. Side to side movement, as shown for example in FIGS. 4 and 5, is largely restricted by the side frames.

As can be seen in FIG. 9B, when the tank is lifted, the cables raise bottom frame member 14, and at the same time collapse the tank 10 from the bottom up until the top frame member 12, cross members 18, and walkway 30 are all lifted as a unit to the top of the gantry.

This lifting can also be seen in FIGS. 10 and 11 where the cables cannot be seen.

FIGS. 10 and 11 show a storage tank 10 in accordance with this invention being raised from a configuration in which liquids are stored in the tank (see FIG. 9A) to a stored configuration in which cargo can be placed in the trailer beneath the collapsed tank. The tank in the liquid receiving configuration is shown in FIGS. 4, 5, and 9, for example. FIG. 10 shows an intermediate position in which the lower frame 14 has been raised by cables 34, 36 to a position where the liquid containing portion has been collapsed and the bottom frame 14 engages the upper gantry platform beams 18 from below. As the lower frame 14 continues to be lifted upward by the cables, it carries the upper frame 12 and upper platform beams 18 with it until it reaches the storage position shown in FIG. 11.

FIG. 12 shows the tank structure raised into a storage position with the dry cargo 80 loaded onto the trailer beneath the collapsed tank. As can be seen, the upper 12 and lower tank 14 frames are drawn into position closely adjacent to each other and adjacent the upper platform beams 18 of the support gantry.

FIG. 13 is a bottom perspective view of an embodiment of the liquid impermeable elastic bladder 100 for a tank 10 which is attached between and supported by upper 12 and lower 14 frame members that are suspended from a gantry 16 that includes a plurality of short vertical supports 17 along each side and an upper gantry platform comprising a plurality of cross beams 18 attached to the upper frame, as described in more detail above. The liquid impermeable elastic bladder is placed within the substantially inelastic flexible fabric outer container 103. The elastic bladder 100 and inelastic flexible fabric outer container 103 include a centrally positioned outlet port 101, two end sections 102, 104 each having a sealable edge 106, 108, respectively and a middle portion 109 having corresponding sealable edges 110, 112. The end sections 102, 104 each include an end wall 114, a top wall 115, a bottom wall 116 and two sidewalls 118, 120. Extending from each corner 122, 124, 126 and 128 of the end wall 114 is a diagonal seal 130, 132, 134, 136 (diagonal seal 136 on sidewall 120 is not shown). The diagonal seals 130, 132, 134, 136 located on the flat surface of the sidewalls 118, 120 and on the top wall 115 eliminates the need for seams or seals along the corner edges of the bladder 100, which are difficult to clean.

To fabricate an end section 102 having the diagonal seals 130, 132, 134, 136, two end panels 140, 142 and a center panel 144 are fabricated and welded together as shown in FIG. 16. That is, a first end panel 140, as shown in FIGS. 14 and 16, is fabricated from a single piece blank 200, as shown in FIG. 15, having two top flaps 202, 204, an end wall portion 206, a sidewall portion 208, a bottom portion 209, and a side flap 210 is folded to define an end panel 140. Dashed lines in FIG. 15 indicate fold lines for the single piece blank 200. The two top flaps 202, 204 are overlapped to form the diagonal seal 132. Together, top flaps 202 and 204 form a portion of top wall 115. The sidewall portion 208 and side flap 210 are overlapped to define the sidewall 118 having diagonal seal 130. A second end panel 142 is similarly fabricated, except in a mirrored configuration, to form the opposite corner of the end section 102. A center panel 144 forming a portion of the top wall 115, a portion of the bottom wall 116, and a portion of the end wall 114 is connected to the end panels 140, 142 along sealable edges of the central panel 146, 148 and of the end panels 150, 152, respectively, to form the end section 102. It should be appreciated by those having ordinary skill in the art that although end sections 102, 104 are each formed from two end panels 140, 142 and a center panel 144, the end sections 102, 104 can be formed from a single piece blank and this modification is intended to be within the spirit and scope of the claims.

The middle portion 109 may also be fabricated from multiple panels, for example, 214, 216, 218, 220 and 222 as shown in FIG. 16, or as a single piece blank depending on the desired size of the middle portion 109 and the size of the material selected. An example of a liquid impermeable elastic material that can be used is urethane approved for use with food grade products including, but not limited to, milk, corn syrup and cooking oils. The middle portion 109 includes a cleaning portal 133 of sufficient size to receive a cleaning person, or automatic or manual cleaning apparatus.

It should be appreciated by those having ordinary skill in the art that end section 104 is fabricated in the same manner as end section 102, except in a mirrored configuration, to form the opposite end of the elastic bladder 100.

To assemble the elastic bladder 100, end sections 102, 104 are first fabricated and sealed and then additional middle portion panels are added to each section 102, 104 to form two bladder end parts. The two end parts are then sealed to center panel 218 to complete the elastic bladder 100. The tooling used to seal the middle portion panels is removed through portal 133 described in more detail above. Each middle portion panel 214, 216, 218, 220, 222 may also have another seal perpendicular to the perimeter edge seals to fabricate the tubular or rectangular panel structure from a flat sheet of material. In an embodiment of the invention, this seal is formed before the perimeter edges of the panels are sealed together and is preferably located on a flat surface of the panel rather than a corner to prevent liquid from collecting in the corner, which is difficult to clean.

All internal seals, including for example with respect to end section 102, the diagonal seals 130, 132, 134, 136, the sealable edges of the panels 146, 148, 150, 152 and the sealable edges of the end section to the middle portion 109, 110 and 108, 112 all include an overlap of approximately 1 inch and are welded by applying RF energy using 3.5 kilowatts of RF power for approximately 14 second at an air pressure of 60 psi to form a 100% solid weld. The seals are allowed to cool for approximately 22 seconds. All the seals and edges are preferably sealed together using either butted joints or lap joints.

As discussed above, the elastic bladder 100 is preferably provided with an enlarged bead 86, as shown in FIG. 8, to prevent the fabric layer from slipping out of the clamp. That is, each end section 102, 104 and the middle portion 109 have a folded over sealed edge forming a compartment for receiving a rope. In an embodiment of the invention, the bottom perimeter edge of the elastic bladder 100 also includes a roped edge to be attached externally to the tank 10 such that the internal surface of the tank 10 has no seams or seals around the top or the bottom perimeter.

As shown in FIGS. 17 through 19B, in an embodiment of the invention, the liquid storage tank 10 includes a substantially inelastic flexible fabric outer container 103 and the liquid impermeable elastic bladder 100 not visible in FIGS. 17 through 19B. The outer container 103 and the elastic bladder 100 have an outlet 300 that is positioned proximate the middle of the trailer. The outlet 300, including outlet port 101, is removeably attached to the discharge piping 302 positioned underneath the trailer floor 304. In the deployed configuration, as shown in FIGS. 17 and 19A, the lower frame 14 is proximate the trailer floor 304. In the emptying configuration, as shown in FIGS. 18A, 18B and 19B, the lower frame 14 is raised approximately six inches from a position on the trailer floor 304 towards the upper frame 12 creating a substantially funnel shaped bottom in the inelastic flexible fabric outer container 103 and the elastic bladder 100 and permitting the liquid to drain out of the elastic bladder 100 via gravity. It should be appreciated that, to lift the lower frame 14 proximate the upper frame 12 in the storage position as shown in FIG. 11, the outlet 300 is first disconnected from the discharge piping 302. Preferably, the lower frame 14 and upper frame 12 are stored proximate the ceiling of the trailer to permit cargo to be stowed underneath as shown in FIG. 12.

There has thus been described collapsible storage tank for use in a freight container for selectively carrying solid freight and bulk liquid freight. Those skilled in the art will recognize that modifications may be made in the apparatus described herein without departing from the true spirit and scope of the invention which accordingly are intended to be limited solely by the appended claims. 

1. A liquid impermeable elastic bladder for a collapsible storage tank for carrying bulk liquid freight comprising: a first and a second end section, each end section having an end wall, two sidewalls, a top wall, a bottom wall, a sealable edge, a diagonal seal extending along each of the two sidewalls from a first and second corner of the end section to the sealable edge, and, two diagonal seals extending along the top wall from a third and forth corner of the end section to the sealable edge; and a middle portion having sealable edges coupled to the sealable edges of the first and second end sections.
 2. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the diagonal seals are each welded together.
 3. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the sealable edges of the first and second end sections are each welded to one of the sealable edges of the middle portion.
 4. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the diagonal seals further comprise a one inch overlap.
 5. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the middle portion comprises multiple panels of an elastic material welded together.
 6. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the sealable edges of the first and second end sections each form butt joints with one of the sealable edges of the middle portion.
 7. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the sealable edges of the first and second end sections each form lap joints with one of the sealable edges of the middle portion.
 8. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein each end section and the middle portion further include a folded over sealed edge forming a compartment for receiving a rope.
 9. The liquid impermeable elastic bladder for a collapsible storage tank of claim 1, wherein the first and second end sections each comprise two end panels coupled to a center panel.
 10. A collapsible liquid storage tank for use in a trailer for selectively carrying solid freight and bulk liquid freight comprising: a substantially rigid gantry having a first plurality of support posts; a first frame; a second frame suspended from the gantry; a substantially inelastic flexible fabric container having side walls connected between the first frame and the second frame; a liquid impermeable elastic bladder having two end sections and a middle portion, each end section having a diagonal seal extending from each corner of an end wall of the end section, the elastic bladder disposed within the fabric container; and a hoist coupled between the gantry and the second frame for lifting the second frame towards the first frame.
 11. The collapsible liquid storage tank of claim 10 further comprising an outlet port centrally positioned within a floor of the liquid impermeable elastic bladder.
 12. The collapsible liquid storage tank of claim 11 wherein the outlet port is removeably attached to discharge piping on a floor of the trailer.
 13. The collapsible liquid storage tank of claim 12 wherein the inelastic flexible fabric container forms a substantially funnel-shaped bottom configuration when the second frame is lifted into an emptying position.
 14. The collapsible liquid storage tank of claim 10 wherein the elastic bladder is collapsed when the second frame is lifted towards the first frame into a storage position.
 15. A collapsible liquid storage tank for use in a trailer for carrying bulk liquid freight comprising: a first frame coupled to the trailer; a second frame coupled to the first frame; a substantially inelastic flexible fabric container having side walls connected between the first frame and the second frame; a liquid impermeable elastic bladder disposed within the fabric container; an outlet centrally positioned within a floor of the liquid impermeable elastic bladder; and a hoist coupled to the first and second frames for lifting the second frame towards the first frame and reducing the spacing between the second frame and the first frame.
 16. The collapsible liquid storage tank of claim 15 wherein the second frame is suspended approximately six inches from a bottom of the trailer towards the first frame into an emptying position.
 17. The collapsible liquid storage tank of claim 16 wherein the outlet port is temporarily fixed to the bottom of the trailer in the emptying position.
 18. The collapsible liquid storage tank of claim 16 wherein the inelastic flexible fabric container forms a substantially funnel-shaped bottom configuration in the emptying position.
 19. The collapsible liquid storage tank of claim 15 wherein the second frame is suspended proximate the first frame in a storage position.
 20. The collapsible liquid storage tank of claim 15 in which the liquid impermeable elastic bladder has a substantially smooth inner surface when not expanded. 